1. Field of the Invention
This invention relates to a method and apparatus for die casting rotor used in a motor, more particularly die casting apparatus for a rotor and method thereof which may eliminate a reworking process such as turning operations and broaching operations, and may simplify a manufacturing process by changing a mold's shape.
2. Prior Art
FIG. 1 is a sectional view partially showing a conventional die casting apparatus.
A conventional die casting apparatus, as shown in FIG. 1, has a stationary die plate 5 and an intermediate die plate 15 at the right side, and a movable die plate 21 and a base die plate 23 at the left side with reference to parting line PL. An extracting plate 10 for extracting the die cast rotor is mounted between the stationary die plate 5 and the intermediate die plate 15.
An insert 4 forming a main passage 3 of molten aluminum is installed in the stationary die plate 5.
A first mold 11 forming an annular first cavity 13 and a plurality of sprues 12 are installed in the intermediate die plate 15. An annular sleeve 31 and a second mold 37 are mounted in the movable die plate 21, and a preform 33 of the rotor is inserted on the second mold 37.
The preform 33 consists of a plurality of circular stacks 34, a central bore 32, and a plurality of circularly arranged openings 35.
A manufacturing process for a rotor using the above-mentioned die casting apparatus will be described below.
The molten aluminum of high temperature and pressure flows from the main passage 3 into an annular first cavity 13 through a plurality of sprues and then into an annular second cavity 39 passing through the openings.
If the molten aluminum is cooled, a die cast rotor is completed.
According to the above-mentioned die casting apparatus, because the molten aluminum is injected into the cavity of the first mold at high pressure, the molten aluminum leaks from the combination part between the first mold and an opposite surface of the movable die plate facing the intermediate die plate. FIG. 2 is a perspective view of a die cast rotor by the conventional die casting apparatus. Referring to the die cast rotor shown in FIG. 2, the leaked molten aluminum is cooled on a upper periphery of the preform 33, which results in forming projections 42.
When the molten aluminum is filled and cooled in the annular first mold 11 and thus the first mold 11 is separated, a small quantity of the molten aluminum is cooled in a projected state along a plurality of sprue gates.
Therefore, a number of projections 45 are formed on an upper surface of the die cast rotor on which the sprue gates have been placed. Furthermore, because the molten aluminum is injected at high temperature and high pressure, an inner diameter of the preform is deformed, thereby concentricity of the die cast rotor may not be uniform. Accordingly, the rotor for a motor which is die cast by conventional die casting apparatus should be reworked by broaching operations and turning operations after die casting operation for precision manufacturing of the inner and outer diameters of the rotor.